Sheave for ratchet block

ABSTRACT

The line-receiving groove of the sheave includes a plurality of opposed inwardly converging shoulders on the sides of the groove and a coplanar corner in the innermost portion of the groove. The configuration is especially adaptable to ratchet blocks in that little effort is required to hold the line against a strong pull, and the line may be easily released in the direction of pull without binding or undue wear.

United States Patent "IIHHL' lll lllt Gilson 1 Feb. 6, 1973 1 SHEAVE FORRATCHET BLOCK 2,749,759 6/1956 Kienhofer ..74/230.24 Inventor: Robert E.Gilson 4 North Franklin 2,922,310 1/1960 Anderson ..74/230.3 Avenue,Madison, Wis. 53713 FOREIGN PATENTS OR APPLICATIONS 1 1 Filedl p 19701,096,059 12/1954 France ..74/230.0l

21 l. N .2 71 56 I 1 App 0 8 Primary ExaminerC. J. l-lusarAttorney-Russell W. Pyle [52] US. Cl. ..74/230.24, 74/230.05, 74/230.5,

74/229, 254/190 R [57] ABSTRACT [51] Int. Cl ..Fl6h 55/36 [58] Field ofSearch....-.-....74/230.01, 230.05, 230.24, g f the i f a 74,2303 229254/190 192' 188/823 827 ralty o oppose lnwar y converglng s on ers onthe sldes of the groove and a coplanar corner m the innermost portion ofthe groove. The configuration is [561 References c'ted especiallyadaptable to ratchet blocks in that little ef- UNITED STATES PATENTSfort is required to hold the line against a strong pull, and the linemay be easily released ln the dlrectlon of 2,875,981 3/1959 Hunter..74/230.0l pull without binding or undue wear, 3,528,645 9/1970 Harken..254/192 3,302,932 2/1967 Wallin ..74/230.5 11 Claims, 4 DrawingFigures SHEAVE FOR RATCHET BLOCK This invention relates to a bearing orpulley blocks for rotatably carrying a flexible line of round crosssection and more particularly to an improvement in the line-carryinggroove in the sheave of such pulley blocks.

In a conventional pulley, a sheave is rotatably mounted in a support,and the sheave is provided with an outer groove adapted for carrying androtatably supporting a flexible line. In order to prevent slippagebetween the line and the sheave, it is known to roughen the groove orprovide sharp edges or teeth therein to increase the sliding frictionbetween the line and sheave. It is also common to employ a groove with aV- shaped configuration, whereby the line is wedged deeper into thegroove as tension on the line is increased.

Additional factors, however, become important in applications where itis necessary to grip the line as well as to allow the line to slip inthe groove of the sheave. An example of such application is a ratchetblock used on sailboats where rotational movement of the sheave is ormay be limited to one direction. The ratchet block allows a line to bedrawn freely in one direction, and friction between the line and sheaveenables controlled slippage of the line over the stationary sheave inthe other direction. The use of roughened surfaces, sharp edges orV-shaped configurations in the groove of ratchet blocks has not provenentirely satisfactory, because of excessive wear on the line and bindingof the line in the groove.

Accordingly, an object of the present invention is to provide a pulleysheave with the capability of positively gripping a line under tensionas well as the capability of releasing the line when tension is eased.

Another object is the provision of such a pulley sheave configurationthat will not cause undue wear on or bind the line.

Other objects will become apparent from the following description andappended claims, taken in connection with the accompanying drawing,wherein:

FIG. 1 is a transverse vertical sectional view, shown partiallydisassembled, of a ratchet block that incorporates features of thepresently described invention;

FIG. 2 is a vertical sectional view taken along section line 2-2 in FIG.1;

FIG. 3 is an isolated plan view of the improved sheave illustrated inFIGS. 1 and 2; and

FIG. 4 is a cross sectional view taken along line 44 of FIG. 3.

In FIGS. 1 and 2,-a particular ratchet block is shown, although it willbe understood that the improved sheave described herein is equallyadaptable to any known rotational support arrangement capable ofpreventing rotation of the sheave or other line carrying member in onedirection. As shown, the block comprises a pair of interconnected sideplates 10 and 12 with an annular sheave 14 rotatably mountedtherebetween. Outer side plates 16 and 18 may be additionally providedfor extra strength.

A shaft between the lower portions of the side plates l and 12 is formedby annular shoulders 20 and 22, projecting toward one another fromrespective side plates and 12 and defining respective annular races uponwhich respective ball bearing sets 24 and 26 are received. Suitablefasteners 28, such as bolts, rivets, or

the like, are provided in the area of the shoulders to hold the sideplates together. The sheave 14 includes a central web 30 extendingradially inward separating adjacent sets of ball bearings 24 and 26.Annular shoulders 32 and 34 on the-sheave define respective outerannular races for the ball bearing sets 24 and 26. The block is designedsuch that the ball bearing sets 24 and 26 contact the inner surfaces oftheir respective adjacent side plates 10 and 12 as well as the inner andouter races. An upper portion of the block may be provided with arotatably and pivotable shackle arrangement generally indicated at 36.

Means are provided to prevent rotation of the sheave in one rotationaldirection, such means taking the form of a cam and ratchet assembly inthe preferred embodiment shown. A plurality of inclined teeth 38 are provided on the innermost portion of the central web 30. A pawl 40 isrotatably mounted intermediate its ends around an axis 42 offset fromthe rotational axis of the sheave 14. One end 44 of the pawl isengageable with the teeth 38, and a coil spring 46 is connected betweenthe pawl and one of the side plates, to resiliently urge said end of thepawl into engagement with the teeth. The other end 48 of the pawl 40 isbeveled for coaction against a round cam 50 eccentrically secured on apin 52 rotatably mounted between the side plates 10 and 12. The pin 52extends externally of one of the side plates to a handle 54, in order toenable rotation of the cam 50 externally of the block.

When the cam 50 is in the position shown, the spring loaded pawl 40 isallowed to contact and resiliently ride over the inclined teeth 38during rotation of the sheave in one direction, in this instance aclockwise direction. Rotation in the other or counterclockwise directionis prevented by engagement of the pawl end 44 between the inclined teeth38. Upon rotation of the cam 50 by turning the handle 54, the end 44 ofthe pawl is rotated away from and withdrawn from engagement with theinclined teeth 36, thereby allowing the sheave to rotate freely in bothdirections.

As best shown in FIGS. 1, 3 and 4, the sheave 14 has an open groove 56in the outer periphery thereof in which a flexible round line 57 isreceived (FIG. 1). The groove 56 is substantially V-shaped and isspecially formed to enable gripping and release of the line withoutencountering the problems hereinbefore described. The groove 56 isshaped in the form of a plurality of identical and interconnectedprismatic notches, with adjacent notches having common trapezoidalbases. The notches are preferably six in number, although other numbersin the range of four to ten notches may be employed.

Each notch comprises opposed flat planar side surfaces, such as 58 and60, and 62 and 64 in the sides of the groove 56, said surfacesconverging inward toward one another and connected by respective flatplanar or concave bottom surfaces 66 and 68 at the bottom of the groove.Adjacent contiguous side surfaces, such as 58 and 62, and 60 and 64,define therebetween opposed inwardly tapering shoulders 72 and 72,respectively, while corresponding adjacent bottom surfaces 66 and 68define a coplanar corner 74 connecting said shoulders at the bottom ofsaid groove, said corner being substantially parallel to the axis ofrotation of the sheave. The inner groove of the sheave thereforecomprises a plurality of interconnected chordal surfaces or portions,such as 66 and 68, which define line-gripping corners 74.

In normal operation, the line is wrapped around 25 to 55 percent of thecircumference of the sheave, such that the line is capable of contactingat least one of the corners 74 when sufficient line tension is applied,whereby the line is firmly gripped. As tension is eased, the linegradually moves out of contact with the corners 74 and rides up betweenthe shoulders 72 and 72, thereby permitting controlled release of theline.

I claim:

1. In a pulley block having a sheave rotatably mounted therein, saidsheave having a line-receiving groove, the improvement wherein the sidesurfaces of said line-receiving groove taper inwardly toward the bottomof said groove, and the bottom of said groove comprises a plurality ofupstanding obtuse comers extending between said side surfaces and spacedaround the circumference of said groove, such that a line received insaid groove rides up between the side surfaces of said groove in theabsence of substantial tension thereon, and said line engages at leastone of said corners under application of tension thereto.

2. The improvement of claim 1 wherein the bottom of said groovecomprises a plurality of interconnected chordal portions that definesaid corners.

3. The improvement of claim 2 wherein the sides of said groove eachcomprise a plurality of interconnected side surfaces defining raisedcorners therebetween, said corners extending radially from the bottom ofsaid groove.

' 4. The improvement of claim 3 wherein adjacent chordal portions at thebottom of said groove and corresponding adjacent surfaces at each sideof the groove are interconnected in substantially the same plane.

5. The improvement of claim 3 wherein said chordal surfaces and saidside surfaces are substantially planar.

6. The improvement of claim 1 wherein'means are provided for limitingrotation of said sheave in one direction.

7. An apparatus for carrying a flexible line comprising a rotatablemember, means for rotatably mounting said member about its axis, and acontinuous groove around the outer surface of said member for receivinga flexible line, the bottom of said groove having a plurality ofupstanding obtuse corners disposed around the circumference thereof,such that a line carried in said groove rides over said corners freelyin the absence of substantial tension thereon and engages and gripsagainst at least one of said corners under application of tensionthereto.

8. The apparatus of claim 7 wherein said corners are at least four innumber and are disposed substantially along a line parallel to the axisof said member.

9. The apparatus of claim 7 wherein means are provided for limitingrotation of said member to one direction.

10. The apparatus of claim 7 wherein said corners are defined byinterconnected chordal surfaces at the bottom of said groove.

11. An apparatus for carrying a flexible line comprising a generallycylindrical member, means for rotatably mounting said member about itsaxis, and a continuous,

inward] ta ered line-receiving groove formed around and wt in hecylindrical surface of said member, said groove having a bottomcomprising interconnected chordal portions defining at least four raisedcorners spaced around the bottom of said groove such that a linereceived therein engages and grips against at least one of said cornersunder application of tension to said line and'rides up in said grooveand away from said corners upon release of tension from said line.

1. In a pulley block having a sheave rotatably mounted therein, saidsheave having a line-receiving groove, the improvement wherein the sidesurfaces of said line-receiving groove taper inwardly toward the bottomof said groove, and the bottom of said groove comprises a plurality ofupstanding obtuse corners extending between said side surfaces andspaced around the circumference of said groove, such that a linereceived in said groove rides up between the side surfaces of saidgroove in the absence of substantial tension thereon, and said lineengages at least one of said corners under application of tensionthereto.
 1. In a pulley block having a sheave rotatably mounted therein,said sheave having a line-receiving groove, the improvement wherein theside surfaces of said line-receiving groove taper inwardly toward thebottom of said groove, and the bottom of said groove comprises aplurality of upstanding obtuse corners extending between said sidesurfaces and spaced around the circumference of said groove, such that aline received in said groove rides up between the side surfaces of saidgroove in the absence of substantial tension thereon, and said lineengages at least one of said corners under application of tensionthereto.
 2. The improvement of claim 1 wherein the bottom of said groovecomprises a plurality of interconnected chordal portions that definesaid corners.
 3. The improvement of claim 2 wherein the sides of saidgroove each comprise a plurality of interconnected side surfacesdefining raised corners therebetween, said corners extending radiallyfrom the bottom of said groove.
 4. The improvement of claim 3 whereinadjacent chordal portions at the bottom of said groove and correspondingadjacent surfaces at each side of the groove are interconnected insubstantially the same plane.
 5. The improvement of claim 3 wherein saidchordal surfaces and said side surfaces are substantially planar.
 6. Theimprovement of claim 1 wherein means are provided for limiting rotationof said sheave in one direction.
 7. An apparatus for carrying a flexibleline comprising a rotatable member, means for rotatably mounting saidmember about its axis, and a continuous groove around the outer surfaceof said member for receiving a flexible line, the bottom of said groovehaving a plurality of upstanding obtuse corners disposed around thecircumference thereof, such that a line carried in said groove ridesover said corners freely in the absence of substantial tension thereonand engages and grips against at least one of said corners underapplication of tension thereto.
 8. The apparatus of claim 7 wherein saidcorners are at least four in number and are disposed substantially alonga line parallel to the axis of said member.
 9. The apparatus of claim 7wherein means are provided for limiting rotation of said member to onedirection.
 10. The apparatus of claim 7 wherein said corners are definedby interconnected chordal surfaces at the bottom of said groove.